1 /**************************************************************************
2 * Copyright(c) 1998-1999, ALICE Experiment at CERN, All rights reserved. *
4 * Author: The ALICE Off-line Project. *
5 * Contributors are mentioned in the code where appropriate. *
7 * Permission to use, copy, modify and distribute this software and its *
8 * documentation strictly for non-commercial purposes is hereby granted *
9 * without fee, provided that the above copyright notice appears in all *
10 * copies and that both the copyright notice and this permission notice *
11 * appear in the supporting documentation. The authors make no claims *
12 * about the suitability of this software for any purpose. It is *
13 * provided "as is" without express or implied warranty. *
14 **************************************************************************/
18 ///////////////////////////////////////////////////////////////////////////////
20 // Implementation of the external track parameterisation class. //
22 // This parameterisation is used to exchange tracks between the detectors. //
23 // A set of functions returning the position and the momentum of tracks //
24 // in the global coordinate system as well as the track impact parameters //
26 // Origin: I.Belikov, CERN, Jouri.Belikov@cern.ch //
27 ///////////////////////////////////////////////////////////////////////////////
31 #include <TMatrixDSym.h>
32 #include <TPolyMarker3D.h>
36 #include "AliExternalTrackParam.h"
37 #include "AliVVertex.h"
40 ClassImp(AliExternalTrackParam)
42 Double32_t AliExternalTrackParam::fgMostProbablePt=kMostProbablePt;
44 //_____________________________________________________________________________
45 AliExternalTrackParam::AliExternalTrackParam() :
51 // default constructor
53 for (Int_t i = 0; i < 5; i++) fP[i] = 0;
54 for (Int_t i = 0; i < 15; i++) fC[i] = 0;
57 //_____________________________________________________________________________
58 AliExternalTrackParam::AliExternalTrackParam(const AliExternalTrackParam &track):
66 for (Int_t i = 0; i < 5; i++) fP[i] = track.fP[i];
67 for (Int_t i = 0; i < 15; i++) fC[i] = track.fC[i];
71 //_____________________________________________________________________________
72 AliExternalTrackParam& AliExternalTrackParam::operator=(const AliExternalTrackParam &trkPar)
75 // assignment operator
79 AliVTrack::operator=(trkPar);
81 fAlpha = trkPar.fAlpha;
83 for (Int_t i = 0; i < 5; i++) fP[i] = trkPar.fP[i];
84 for (Int_t i = 0; i < 15; i++) fC[i] = trkPar.fC[i];
91 //_____________________________________________________________________________
92 AliExternalTrackParam::AliExternalTrackParam(Double_t x, Double_t alpha,
93 const Double_t param[5],
94 const Double_t covar[15]) :
100 // create external track parameters from given arguments
102 for (Int_t i = 0; i < 5; i++) fP[i] = param[i];
103 for (Int_t i = 0; i < 15; i++) fC[i] = covar[i];
107 //_____________________________________________________________________________
108 AliExternalTrackParam::AliExternalTrackParam(const AliVTrack *vTrack) :
114 // Constructor from virtual track,
115 // This is not a copy contructor !
118 if (vTrack->InheritsFrom("AliExternalTrackParam")) {
119 AliError("This is not a copy constructor. Use AliExternalTrackParam(const AliExternalTrackParam &) !");
120 AliWarning("Calling the default constructor...");
121 AliExternalTrackParam();
125 Double_t xyz[3],pxpypz[3],cv[21];
127 pxpypz[0]=vTrack->Px();
128 pxpypz[1]=vTrack->Py();
129 pxpypz[2]=vTrack->Pz();
130 vTrack->GetCovarianceXYZPxPyPz(cv);
131 Short_t sign = (Short_t)vTrack->Charge();
133 Set(xyz,pxpypz,cv,sign);
136 //_____________________________________________________________________________
137 AliExternalTrackParam::AliExternalTrackParam(Double_t xyz[3],Double_t pxpypz[3],
138 Double_t cv[21],Short_t sign) :
144 // constructor from the global parameters
147 Set(xyz,pxpypz,cv,sign);
150 //_____________________________________________________________________________
151 void AliExternalTrackParam::Set(Double_t xyz[3],Double_t pxpypz[3],
152 Double_t cv[21],Short_t sign)
155 // create external track parameters from the global parameters
156 // x,y,z,px,py,pz and their 6x6 covariance matrix
157 // A.Dainese 10.10.08
159 // Calculate alpha: the rotation angle of the corresponding local system.
161 // For global radial position inside the beam pipe, alpha is the
162 // azimuthal angle of the momentum projected on (x,y).
164 // For global radial position outside the ITS, alpha is the
165 // azimuthal angle of the centre of the TPC sector in which the point
168 const double kSafe = 1e-5;
169 Double_t radPos2 = xyz[0]*xyz[0]+xyz[1]*xyz[1];
170 Double_t radMax = 45.; // approximately ITS outer radius
171 if (radPos2 < radMax*radMax) { // inside the ITS
172 fAlpha = TMath::ATan2(pxpypz[1],pxpypz[0]);
173 } else { // outside the ITS
174 Float_t phiPos = TMath::Pi()+TMath::ATan2(-xyz[1], -xyz[0]);
176 TMath::DegToRad()*(20*((((Int_t)(phiPos*TMath::RadToDeg()))/20))+10);
179 Double_t cs=TMath::Cos(fAlpha), sn=TMath::Sin(fAlpha);
180 // protection: avoid alpha being too close to 0 or +-pi/2
181 if (TMath::Abs(sn)<kSafe) {
183 cs=TMath::Cos(fAlpha);
184 sn=TMath::Sin(fAlpha);
187 fAlpha -= TMath::Sign(kSafe, fAlpha);
188 cs=TMath::Cos(fAlpha);
189 sn=TMath::Sin(fAlpha);
191 // Get the vertex of origin and the momentum
192 TVector3 ver(xyz[0],xyz[1],xyz[2]);
193 TVector3 mom(pxpypz[0],pxpypz[1],pxpypz[2]);
195 // avoid momenta along axis
196 if (TMath::Abs(mom[0])<kSafe) mom[0] = TMath::Sign(kSafe*TMath::Abs(mom[1]), mom[0]);
197 if (TMath::Abs(mom[1])<kSafe) mom[1] = TMath::Sign(kSafe*TMath::Abs(mom[0]), mom[1]);
199 // Rotate to the local coordinate system
200 ver.RotateZ(-fAlpha);
201 mom.RotateZ(-fAlpha);
203 // x of the reference plane
206 Double_t charge = (Double_t)sign;
210 fP[2] = TMath::Sin(mom.Phi());
211 fP[3] = mom.Pz()/mom.Pt();
212 fP[4] = TMath::Sign(1/mom.Pt(),charge);
214 // Covariance matrix (formulas to be simplified)
216 Double_t pt=1./TMath::Abs(fP[4]);
217 Double_t r=TMath::Sqrt((1.-fP[2])*(1.+fP[2]));
219 Double_t m00=-sn;// m10=cs;
220 Double_t m23=-pt*(sn + fP[2]*cs/r), m43=-pt*pt*(r*cs - fP[2]*sn);
221 Double_t m24= pt*(cs - fP[2]*sn/r), m44=-pt*pt*(r*sn + fP[2]*cs);
222 Double_t m35=pt, m45=-pt*pt*fP[3];
228 Double_t cv34 = TMath::Sqrt(cv[3 ]*cv[3 ]+cv[4 ]*cv[4 ]);
229 Double_t a1=cv[13]-cv[9]*(m23*m44+m43*m24)/m23/m43;
230 Double_t a2=m23*m24-m23*(m23*m44+m43*m24)/m43;
231 Double_t a3=m43*m44-m43*(m23*m44+m43*m24)/m23;
232 Double_t a4=cv[14]-2.*cv[9]*m24*m44/m23/m43;
233 Double_t a5=m24*m24-2.*m24*m44*m23/m43;
234 Double_t a6=m44*m44-2.*m24*m44*m43/m23;
236 fC[0 ] = cv[0 ]+cv[2 ];
237 fC[1 ] = TMath::Sign(cv34,cv[3 ]/m00);
239 fC[3 ] = (cv[10]/m44-cv[6]/m43)/(m24/m44-m23/m43)/m00;
240 fC[10] = (cv[6]/m00-fC[3 ]*m23)/m43;
241 fC[6 ] = (cv[15]/m00-fC[10]*m45)/m35;
242 fC[4 ] = (cv[12]-cv[8]*m44/m43)/(m24-m23*m44/m43);
243 fC[11] = (cv[8]-fC[4]*m23)/m43;
244 fC[7 ] = cv[17]/m35-fC[11]*m45/m35;
245 fC[5 ] = TMath::Abs((a4-a6*a1/a3)/(a5-a6*a2/a3));
246 fC[14] = TMath::Abs(a1/a3-a2*fC[5]/a3);
247 fC[12] = (cv[9]-fC[5]*m23*m23-fC[14]*m43*m43)/m23/m43;
248 Double_t b1=cv[18]-fC[12]*m23*m45-fC[14]*m43*m45;
251 Double_t b4=cv[19]-fC[12]*m24*m45-fC[14]*m44*m45;
254 fC[8 ] = (b4-b6*b1/b3)/(b5-b6*b2/b3);
255 fC[13] = b1/b3-b2*fC[8]/b3;
256 fC[9 ] = TMath::Abs((cv[20]-fC[14]*(m45*m45)-fC[13]*2.*m35*m45)/(m35*m35));
263 //_____________________________________________________________________________
264 void AliExternalTrackParam::Reset() {
266 // Resets all the parameters to 0
269 for (Int_t i = 0; i < 5; i++) fP[i] = 0;
270 for (Int_t i = 0; i < 15; i++) fC[i] = 0;
273 //_____________________________________________________________________________
274 void AliExternalTrackParam::AddCovariance(const Double_t c[15]) {
276 // Add "something" to the track covarince matrix.
277 // May be needed to account for unknown mis-calibration/mis-alignment
280 fC[1] +=c[1]; fC[2] +=c[2];
281 fC[3] +=c[3]; fC[4] +=c[4]; fC[5] +=c[5];
282 fC[6] +=c[6]; fC[7] +=c[7]; fC[8] +=c[8]; fC[9] +=c[9];
283 fC[10]+=c[10]; fC[11]+=c[11]; fC[12]+=c[12]; fC[13]+=c[13]; fC[14]+=c[14];
288 Double_t AliExternalTrackParam::GetP() const {
289 //---------------------------------------------------------------------
290 // This function returns the track momentum
291 // Results for (nearly) straight tracks are meaningless !
292 //---------------------------------------------------------------------
293 if (TMath::Abs(fP[4])<=kAlmost0) return kVeryBig;
294 return TMath::Sqrt(1.+ fP[3]*fP[3])/TMath::Abs(fP[4]);
297 Double_t AliExternalTrackParam::Get1P() const {
298 //---------------------------------------------------------------------
299 // This function returns the 1/(track momentum)
300 //---------------------------------------------------------------------
301 return TMath::Abs(fP[4])/TMath::Sqrt(1.+ fP[3]*fP[3]);
304 //_______________________________________________________________________
305 Double_t AliExternalTrackParam::GetD(Double_t x,Double_t y,Double_t b) const {
306 //------------------------------------------------------------------
307 // This function calculates the transverse impact parameter
308 // with respect to a point with global coordinates (x,y)
309 // in the magnetic field "b" (kG)
310 //------------------------------------------------------------------
311 if (TMath::Abs(b) < kAlmost0Field) return GetLinearD(x,y);
312 Double_t rp4=GetC(b);
314 Double_t xt=fX, yt=fP[0];
316 Double_t sn=TMath::Sin(fAlpha), cs=TMath::Cos(fAlpha);
317 Double_t a = x*cs + y*sn;
318 y = -x*sn + y*cs; x=a;
321 sn=rp4*xt - fP[2]; cs=rp4*yt + TMath::Sqrt((1.- fP[2])*(1.+fP[2]));
322 a=2*(xt*fP[2] - yt*TMath::Sqrt((1.-fP[2])*(1.+fP[2])))-rp4*(xt*xt + yt*yt);
323 return -a/(1 + TMath::Sqrt(sn*sn + cs*cs));
326 //_______________________________________________________________________
327 void AliExternalTrackParam::
328 GetDZ(Double_t x, Double_t y, Double_t z, Double_t b, Float_t dz[2]) const {
329 //------------------------------------------------------------------
330 // This function calculates the transverse and longitudinal impact parameters
331 // with respect to a point with global coordinates (x,y)
332 // in the magnetic field "b" (kG)
333 //------------------------------------------------------------------
334 Double_t f1 = fP[2], r1 = TMath::Sqrt((1.-f1)*(1.+f1));
335 Double_t xt=fX, yt=fP[0];
336 Double_t sn=TMath::Sin(fAlpha), cs=TMath::Cos(fAlpha);
337 Double_t a = x*cs + y*sn;
338 y = -x*sn + y*cs; x=a;
341 Double_t rp4=GetC(b);
342 if ((TMath::Abs(b) < kAlmost0Field) || (TMath::Abs(rp4) < kAlmost0)) {
343 dz[0] = -(xt*f1 - yt*r1);
344 dz[1] = fP[1] + (dz[0]*f1 - xt)/r1*fP[3] - z;
348 sn=rp4*xt - f1; cs=rp4*yt + r1;
349 a=2*(xt*f1 - yt*r1)-rp4*(xt*xt + yt*yt);
350 Double_t rr=TMath::Sqrt(sn*sn + cs*cs);
352 Double_t f2 = -sn/rr, r2 = TMath::Sqrt((1.-f2)*(1.+f2));
353 dz[1] = fP[1] + fP[3]/rp4*TMath::ASin(f2*r1 - f1*r2) - z;
356 //_______________________________________________________________________
357 Double_t AliExternalTrackParam::GetLinearD(Double_t xv,Double_t yv) const {
358 //------------------------------------------------------------------
359 // This function calculates the transverse impact parameter
360 // with respect to a point with global coordinates (xv,yv)
361 // neglecting the track curvature.
362 //------------------------------------------------------------------
363 Double_t sn=TMath::Sin(fAlpha), cs=TMath::Cos(fAlpha);
364 Double_t x= xv*cs + yv*sn;
365 Double_t y=-xv*sn + yv*cs;
367 Double_t d = (fX-x)*fP[2] - (fP[0]-y)*TMath::Sqrt((1.-fP[2])*(1.+fP[2]));
372 Bool_t AliExternalTrackParam::CorrectForMeanMaterialdEdx
373 (Double_t xOverX0, Double_t xTimesRho, Double_t mass,
376 //------------------------------------------------------------------
377 // This function corrects the track parameters for the crossed material.
378 // "xOverX0" - X/X0, the thickness in units of the radiation length.
379 // "xTimesRho" - is the product length*density (g/cm^2).
380 // "mass" - the mass of this particle (GeV/c^2).
381 // "dEdx" - mean enery loss (GeV/(g/cm^2)
382 // "anglecorr" - switch for the angular correction
383 //------------------------------------------------------------------
388 Double_t &fC22=fC[5];
389 Double_t &fC33=fC[9];
390 Double_t &fC43=fC[13];
391 Double_t &fC44=fC[14];
393 //Apply angle correction, if requested
395 Double_t angle=TMath::Sqrt((1.+ fP3*fP3)/((1-fP2)*(1.+fP2)));
402 Double_t beta2=p2/(p2 + mass*mass);
404 //Calculating the multiple scattering corrections******************
410 Double_t theta2=14.1*14.1/(beta2*p2*1e6)*TMath::Abs(xOverX0);
411 //Double_t theta2=1.0259e-6*14*14/28/(beta2*p2)*TMath::Abs(d)*9.36*2.33;
412 if(theta2>TMath::Pi()*TMath::Pi()) return kFALSE;
413 cC22 = theta2*((1.-fP2)*(1.+fP2))*(1. + fP3*fP3);
414 cC33 = theta2*(1. + fP3*fP3)*(1. + fP3*fP3);
415 cC43 = theta2*fP3*fP4*(1. + fP3*fP3);
416 cC44 = theta2*fP3*fP4*fP3*fP4;
419 //Calculating the energy loss corrections************************
421 if ((xTimesRho != 0.) && (beta2 < 1.)) {
422 Double_t dE=dEdx*xTimesRho;
423 Double_t e=TMath::Sqrt(p2 + mass*mass);
424 if ( TMath::Abs(dE) > 0.3*e ) return kFALSE; //30% energy loss is too much!
425 //cP4 = (1.- e/p2*dE);
426 if ( (1.+ dE/p2*(dE + 2*e)) < 0. ) return kFALSE;
427 cP4 = 1./TMath::Sqrt(1.+ dE/p2*(dE + 2*e)); //A precise formula by Ruben !
428 if (TMath::Abs(fP4*cP4)>100.) return kFALSE; //Do not track below 10 MeV/c
431 // Approximate energy loss fluctuation (M.Ivanov)
432 const Double_t knst=0.07; // To be tuned.
433 Double_t sigmadE=knst*TMath::Sqrt(TMath::Abs(dE));
434 cC44 += ((sigmadE*e/p2*fP4)*(sigmadE*e/p2*fP4));
438 //Applying the corrections*****************************
450 Bool_t AliExternalTrackParam::CorrectForMeanMaterial
451 (Double_t xOverX0, Double_t xTimesRho, Double_t mass,
453 Double_t (*Bethe)(Double_t)) {
454 //------------------------------------------------------------------
455 // This function corrects the track parameters for the crossed material.
456 // "xOverX0" - X/X0, the thickness in units of the radiation length.
457 // "xTimesRho" - is the product length*density (g/cm^2).
458 // "mass" - the mass of this particle (GeV/c^2).
459 // "anglecorr" - switch for the angular correction
460 // "Bethe" - function calculating the energy loss (GeV/(g/cm^2))
461 //------------------------------------------------------------------
463 Double_t bg=GetP()/mass;
464 Double_t dEdx=Bethe(bg);
466 return CorrectForMeanMaterialdEdx(xOverX0,xTimesRho,mass,dEdx,anglecorr);
469 Bool_t AliExternalTrackParam::CorrectForMeanMaterialZA
470 (Double_t xOverX0, Double_t xTimesRho, Double_t mass,
477 //------------------------------------------------------------------
478 // This function corrects the track parameters for the crossed material
479 // using the full Geant-like Bethe-Bloch formula parameterization
480 // "xOverX0" - X/X0, the thickness in units of the radiation length.
481 // "xTimesRho" - is the product length*density (g/cm^2).
482 // "mass" - the mass of this particle (GeV/c^2).
483 // "density" - mean density (g/cm^3)
484 // "zOverA" - mean Z/A
485 // "exEnergy" - mean exitation energy (GeV)
486 // "jp1" - density effect first junction point
487 // "jp2" - density effect second junction point
488 // "anglecorr" - switch for the angular correction
490 // The default values of the parameters are for silicon
492 //------------------------------------------------------------------
494 Double_t bg=GetP()/mass;
495 Double_t dEdx=BetheBlochGeant(bg,density,jp1,jp2,exEnergy,zOverA);
497 return CorrectForMeanMaterialdEdx(xOverX0,xTimesRho,mass,dEdx,anglecorr);
502 Bool_t AliExternalTrackParam::CorrectForMaterial
503 (Double_t d, Double_t x0, Double_t mass, Double_t (*Bethe)(Double_t)) {
504 //------------------------------------------------------------------
505 // Deprecated function !
506 // Better use CorrectForMeanMaterial instead of it.
508 // This function corrects the track parameters for the crossed material
509 // "d" - the thickness (fraction of the radiation length)
510 // "x0" - the radiation length (g/cm^2)
511 // "mass" - the mass of this particle (GeV/c^2)
512 //------------------------------------------------------------------
514 return CorrectForMeanMaterial(d,x0*d,mass,kTRUE,Bethe);
518 Double_t AliExternalTrackParam::BetheBlochAleph(Double_t bg,
525 // This is the empirical ALEPH parameterization of the Bethe-Bloch formula.
526 // It is normalized to 1 at the minimum.
530 // The default values for the kp* parameters are for ALICE TPC.
531 // The returned value is in MIP units
534 Double_t beta = bg/TMath::Sqrt(1.+ bg*bg);
536 Double_t aa = TMath::Power(beta,kp4);
537 Double_t bb = TMath::Power(1./bg,kp5);
539 bb=TMath::Log(kp3+bb);
541 return (kp2-aa-bb)*kp1/aa;
544 Double_t AliExternalTrackParam::BetheBlochGeant(Double_t bg,
551 // This is the parameterization of the Bethe-Bloch formula inspired by Geant.
554 // kp0 - density [g/cm^3]
555 // kp1 - density effect first junction point
556 // kp2 - density effect second junction point
557 // kp3 - mean excitation energy [GeV]
560 // The default values for the kp* parameters are for silicon.
561 // The returned value is in [GeV/(g/cm^2)].
564 const Double_t mK = 0.307075e-3; // [GeV*cm^2/g]
565 const Double_t me = 0.511e-3; // [GeV/c^2]
566 const Double_t rho = kp0;
567 const Double_t x0 = kp1*2.303;
568 const Double_t x1 = kp2*2.303;
569 const Double_t mI = kp3;
570 const Double_t mZA = kp4;
571 const Double_t bg2 = bg*bg;
572 const Double_t maxT= 2*me*bg2; // neglecting the electron mass
576 const Double_t x=TMath::Log(bg);
577 const Double_t lhwI=TMath::Log(28.816*1e-9*TMath::Sqrt(rho*mZA)/mI);
581 const Double_t r=(x1-x)/(x1-x0);
582 d2 = lhwI + x - 0.5 + (0.5 - lhwI - x0)*r*r*r;
585 return mK*mZA*(1+bg2)/bg2*
586 (0.5*TMath::Log(2*me*bg2*maxT/(mI*mI)) - bg2/(1+bg2) - d2);
589 Double_t AliExternalTrackParam::BetheBlochSolid(Double_t bg) {
590 //------------------------------------------------------------------
591 // This is an approximation of the Bethe-Bloch formula,
592 // reasonable for solid materials.
593 // All the parameters are, in fact, for Si.
594 // The returned value is in [GeV/(g/cm^2)]
595 //------------------------------------------------------------------
597 return BetheBlochGeant(bg);
600 Double_t AliExternalTrackParam::BetheBlochGas(Double_t bg) {
601 //------------------------------------------------------------------
602 // This is an approximation of the Bethe-Bloch formula,
603 // reasonable for gas materials.
604 // All the parameters are, in fact, for Ne.
605 // The returned value is in [GeV/(g/cm^2)]
606 //------------------------------------------------------------------
608 const Double_t rho = 0.9e-3;
609 const Double_t x0 = 2.;
610 const Double_t x1 = 4.;
611 const Double_t mI = 140.e-9;
612 const Double_t mZA = 0.49555;
614 return BetheBlochGeant(bg,rho,x0,x1,mI,mZA);
617 Bool_t AliExternalTrackParam::Rotate(Double_t alpha) {
618 //------------------------------------------------------------------
619 // Transform this track to the local coord. system rotated
620 // by angle "alpha" (rad) with respect to the global coord. system.
621 //------------------------------------------------------------------
622 if (TMath::Abs(fP[2]) >= kAlmost1) {
623 AliError(Form("Precondition is not satisfied: |sin(phi)|>1 ! %f",fP[2]));
627 if (alpha < -TMath::Pi()) alpha += 2*TMath::Pi();
628 else if (alpha >= TMath::Pi()) alpha -= 2*TMath::Pi();
632 Double_t &fC00=fC[0];
633 Double_t &fC10=fC[1];
634 Double_t &fC20=fC[3];
635 Double_t &fC21=fC[4];
636 Double_t &fC22=fC[5];
637 Double_t &fC30=fC[6];
638 Double_t &fC32=fC[8];
639 Double_t &fC40=fC[10];
640 Double_t &fC42=fC[12];
643 Double_t ca=TMath::Cos(alpha-fAlpha), sa=TMath::Sin(alpha-fAlpha);
644 Double_t sf=fP2, cf=TMath::Sqrt((1.- fP2)*(1.+fP2)); // Improve precision
646 Double_t tmp=sf*ca - cf*sa;
647 if (TMath::Abs(tmp) >= kAlmost1) {
648 if (TMath::Abs(tmp) > 1.+ Double_t(FLT_EPSILON))
649 AliWarning(Form("Rotation failed ! %.10e",tmp));
658 if (TMath::Abs(cf)<kAlmost0) {
659 AliError(Form("Too small cosine value %f",cf));
663 Double_t rr=(ca+sf/cf*sa);
680 Bool_t AliExternalTrackParam::PropagateTo(Double_t xk, Double_t b) {
681 //----------------------------------------------------------------
682 // Propagate this track to the plane X=xk (cm) in the field "b" (kG)
683 //----------------------------------------------------------------
685 if (TMath::Abs(dx)<=kAlmost0) return kTRUE;
687 Double_t crv=GetC(b);
688 if (TMath::Abs(b) < kAlmost0Field) crv=0.;
690 Double_t x2r = crv*dx;
691 Double_t f1=fP[2], f2=f1 + x2r;
692 if (TMath::Abs(f1) >= kAlmost1) return kFALSE;
693 if (TMath::Abs(f2) >= kAlmost1) return kFALSE;
694 if (TMath::Abs(fP[4])< kAlmost0) return kFALSE;
696 Double_t &fP0=fP[0], &fP1=fP[1], &fP2=fP[2], &fP3=fP[3], &fP4=fP[4];
699 &fC10=fC[1], &fC11=fC[2],
700 &fC20=fC[3], &fC21=fC[4], &fC22=fC[5],
701 &fC30=fC[6], &fC31=fC[7], &fC32=fC[8], &fC33=fC[9],
702 &fC40=fC[10], &fC41=fC[11], &fC42=fC[12], &fC43=fC[13], &fC44=fC[14];
704 Double_t r1=TMath::Sqrt((1.-f1)*(1.+f1)), r2=TMath::Sqrt((1.-f2)*(1.+f2));
705 if (TMath::Abs(r1)<kAlmost0) return kFALSE;
706 if (TMath::Abs(r2)<kAlmost0) return kFALSE;
709 double dy2dx = (f1+f2)/(r1+r2);
711 if (TMath::Abs(x2r)<0.05) {
712 fP1 += dx*(r2 + f2*dy2dx)*fP3; // Many thanks to P.Hristov !
716 // for small dx/R the linear apporximation of the arc by the segment is OK,
717 // but at large dx/R the error is very large and leads to incorrect Z propagation
718 // angle traversed delta = 2*asin(dist_start_end / R / 2), hence the arc is: R*deltaPhi
719 // The dist_start_end is obtained from sqrt(dx^2+dy^2) = x/(r1+r2)*sqrt(2+f1*f2+r1*r2)
720 // Similarly, the rotation angle in linear in dx only for dx<<R
721 double chord = dx*TMath::Sqrt(1+dy2dx*dy2dx); // distance from old position to new one
722 double rot = 2*TMath::ASin(0.5*chord*crv); // angular difference seen from the circle center
724 fP2 = TMath::Sin(rot + TMath::ASin(fP2));
729 Double_t f02= dx/(r1*r1*r1); Double_t cc=crv/fP4;
730 Double_t f04=0.5*dx*dx/(r1*r1*r1); f04*=cc;
731 Double_t f12= dx*fP3*f1/(r1*r1*r1);
732 Double_t f14=0.5*dx*dx*fP3*f1/(r1*r1*r1); f14*=cc;
734 Double_t f24= dx; f24*=cc;
737 Double_t b00=f02*fC20 + f04*fC40, b01=f12*fC20 + f14*fC40 + f13*fC30;
738 Double_t b02=f24*fC40;
739 Double_t b10=f02*fC21 + f04*fC41, b11=f12*fC21 + f14*fC41 + f13*fC31;
740 Double_t b12=f24*fC41;
741 Double_t b20=f02*fC22 + f04*fC42, b21=f12*fC22 + f14*fC42 + f13*fC32;
742 Double_t b22=f24*fC42;
743 Double_t b40=f02*fC42 + f04*fC44, b41=f12*fC42 + f14*fC44 + f13*fC43;
744 Double_t b42=f24*fC44;
745 Double_t b30=f02*fC32 + f04*fC43, b31=f12*fC32 + f14*fC43 + f13*fC33;
746 Double_t b32=f24*fC43;
749 Double_t a00=f02*b20+f04*b40,a01=f02*b21+f04*b41,a02=f02*b22+f04*b42;
750 Double_t a11=f12*b21+f14*b41+f13*b31,a12=f12*b22+f14*b42+f13*b32;
751 Double_t a22=f24*b42;
753 //F*C*Ft = C + (b + bt + a)
754 fC00 += b00 + b00 + a00;
755 fC10 += b10 + b01 + a01;
756 fC20 += b20 + b02 + a02;
759 fC11 += b11 + b11 + a11;
760 fC21 += b21 + b12 + a12;
763 fC22 += b22 + b22 + a22;
773 AliExternalTrackParam::Propagate(Double_t alpha, Double_t x, Double_t b) {
774 //------------------------------------------------------------------
775 // Transform this track to the local coord. system rotated
776 // by angle "alpha" (rad) with respect to the global coord. system,
777 // and propagate this track to the plane X=xk (cm) in the field "b" (kG)
778 //------------------------------------------------------------------
780 //Save the parameters
783 Double_t ps[5], cs[15];
784 for (Int_t i=0; i<5; i++) ps[i]=fP[i];
785 for (Int_t i=0; i<15; i++) cs[i]=fC[i];
788 if (PropagateTo(x,b)) return kTRUE;
790 //Restore the parameters, if the operation failed
793 for (Int_t i=0; i<5; i++) fP[i]=ps[i];
794 for (Int_t i=0; i<15; i++) fC[i]=cs[i];
798 Bool_t AliExternalTrackParam::PropagateBxByBz
799 (Double_t alpha, Double_t x, Double_t b[3]) {
800 //------------------------------------------------------------------
801 // Transform this track to the local coord. system rotated
802 // by angle "alpha" (rad) with respect to the global coord. system,
803 // and propagate this track to the plane X=xk (cm),
804 // taking into account all three components of the B field, "b[3]" (kG)
805 //------------------------------------------------------------------
807 //Save the parameters
810 Double_t ps[5], cs[15];
811 for (Int_t i=0; i<5; i++) ps[i]=fP[i];
812 for (Int_t i=0; i<15; i++) cs[i]=fC[i];
815 if (PropagateToBxByBz(x,b)) return kTRUE;
817 //Restore the parameters, if the operation failed
820 for (Int_t i=0; i<5; i++) fP[i]=ps[i];
821 for (Int_t i=0; i<15; i++) fC[i]=cs[i];
826 void AliExternalTrackParam::Propagate(Double_t len, Double_t x[3],
827 Double_t p[3], Double_t bz) const {
828 //+++++++++++++++++++++++++++++++++++++++++
829 // Origin: K. Shileev (Kirill.Shileev@cern.ch)
830 // Extrapolate track along simple helix in magnetic field
831 // Arguments: len -distance alogn helix, [cm]
832 // bz - mag field, [kGaus]
833 // Returns: x and p contain extrapolated positon and momentum
834 // The momentum returned for straight-line tracks is meaningless !
835 //+++++++++++++++++++++++++++++++++++++++++
838 if (OneOverPt() < kAlmost0 || TMath::Abs(bz) < kAlmost0Field || GetC(bz) < kAlmost0){ //straight-line tracks
839 Double_t unit[3]; GetDirection(unit);
844 p[0]=unit[0]/kAlmost0;
845 p[1]=unit[1]/kAlmost0;
846 p[2]=unit[2]/kAlmost0;
850 Double_t a = -kB2C*bz*GetSign();
852 x[0] += p[0]*TMath::Sin(rho*len)/a - p[1]*(1-TMath::Cos(rho*len))/a;
853 x[1] += p[1]*TMath::Sin(rho*len)/a + p[0]*(1-TMath::Cos(rho*len))/a;
857 p[0] = p0 *TMath::Cos(rho*len) - p[1]*TMath::Sin(rho*len);
858 p[1] = p[1]*TMath::Cos(rho*len) + p0 *TMath::Sin(rho*len);
862 Bool_t AliExternalTrackParam::Intersect(Double_t pnt[3], Double_t norm[3],
864 //+++++++++++++++++++++++++++++++++++++++++
865 // Origin: K. Shileev (Kirill.Shileev@cern.ch)
866 // Finds point of intersection (if exists) of the helix with the plane.
867 // Stores result in fX and fP.
868 // Arguments: planePoint,planeNorm - the plane defined by any plane's point
869 // and vector, normal to the plane
870 // Returns: kTrue if helix intersects the plane, kFALSE otherwise.
871 //+++++++++++++++++++++++++++++++++++++++++
872 Double_t x0[3]; GetXYZ(x0); //get track position in MARS
874 //estimates initial helix length up to plane
876 (pnt[0]-x0[0])*norm[0] + (pnt[1]-x0[1])*norm[1] + (pnt[2]-x0[2])*norm[2];
877 Double_t dist=99999,distPrev=dist;
879 while(TMath::Abs(dist)>0.00001){
880 //calculates helix at the distance s from x0 ALONG the helix
883 //distance between current helix position and plane
884 dist=(x[0]-pnt[0])*norm[0]+(x[1]-pnt[1])*norm[1]+(x[2]-pnt[2])*norm[2];
886 if(TMath::Abs(dist) >= TMath::Abs(distPrev)) {return kFALSE;}
890 //on exit pnt is intersection point,norm is track vector at that point,
892 for (Int_t i=0; i<3; i++) {pnt[i]=x[i]; norm[i]=p[i];}
897 AliExternalTrackParam::GetPredictedChi2(Double_t p[2],Double_t cov[3]) const {
898 //----------------------------------------------------------------
899 // Estimate the chi2 of the space point "p" with the cov. matrix "cov"
900 //----------------------------------------------------------------
901 Double_t sdd = fC[0] + cov[0];
902 Double_t sdz = fC[1] + cov[1];
903 Double_t szz = fC[2] + cov[2];
904 Double_t det = sdd*szz - sdz*sdz;
906 if (TMath::Abs(det) < kAlmost0) return kVeryBig;
908 Double_t d = fP[0] - p[0];
909 Double_t z = fP[1] - p[1];
911 return (d*szz*d - 2*d*sdz*z + z*sdd*z)/det;
914 Double_t AliExternalTrackParam::
915 GetPredictedChi2(Double_t p[3],Double_t covyz[3],Double_t covxyz[3]) const {
916 //----------------------------------------------------------------
917 // Estimate the chi2 of the 3D space point "p" and
918 // the full covariance matrix "covyz" and "covxyz"
920 // Cov(x,x) ... : covxyz[0]
921 // Cov(y,x) ... : covxyz[1] covyz[0]
922 // Cov(z,x) ... : covxyz[2] covyz[1] covyz[2]
923 //----------------------------------------------------------------
932 if (TMath::Abs(f) >= kAlmost1) return kVeryBig;
933 Double_t r=TMath::Sqrt((1.-f)*(1.+f));
934 Double_t a=f/r, b=GetTgl()/r;
936 Double_t s2=333.*333.; //something reasonably big (cm^2)
939 v(0,0)= s2; v(0,1)= a*s2; v(0,2)= b*s2;;
940 v(1,0)=a*s2; v(1,1)=a*a*s2 + GetSigmaY2(); v(1,2)=a*b*s2 + GetSigmaZY();
941 v(2,0)=b*s2; v(2,1)=a*b*s2 + GetSigmaZY(); v(2,2)=b*b*s2 + GetSigmaZ2();
943 v(0,0)+=covxyz[0]; v(0,1)+=covxyz[1]; v(0,2)+=covxyz[2];
944 v(1,0)+=covxyz[1]; v(1,1)+=covyz[0]; v(1,2)+=covyz[1];
945 v(2,0)+=covxyz[2]; v(2,1)+=covyz[1]; v(2,2)+=covyz[2];
948 if (!v.IsValid()) return kVeryBig;
951 for (Int_t i = 0; i < 3; i++)
952 for (Int_t j = 0; j < 3; j++) chi2 += res[i]*res[j]*v(i,j);
957 Double_t AliExternalTrackParam::
958 GetPredictedChi2(const AliExternalTrackParam *t) const {
959 //----------------------------------------------------------------
960 // Estimate the chi2 (5 dof) of this track with respect to the track
961 // given by the argument.
962 // The two tracks must be in the same reference system
963 // and estimated at the same reference plane.
964 //----------------------------------------------------------------
966 if (TMath::Abs(1. - t->GetAlpha()/GetAlpha()) > FLT_EPSILON) {
967 AliError("The reference systems of the tracks differ !");
970 if (TMath::Abs(1. - t->GetX()/GetX()) > FLT_EPSILON) {
971 AliError("The reference of the tracks planes differ !");
977 c(1,0)=GetSigmaZY(); c(1,1)=GetSigmaZ2();
978 c(2,0)=GetSigmaSnpY(); c(2,1)=GetSigmaSnpZ(); c(2,2)=GetSigmaSnp2();
979 c(3,0)=GetSigmaTglY(); c(3,1)=GetSigmaTglZ(); c(3,2)=GetSigmaTglSnp(); c(3,3)=GetSigmaTgl2();
980 c(4,0)=GetSigma1PtY(); c(4,1)=GetSigma1PtZ(); c(4,2)=GetSigma1PtSnp(); c(4,3)=GetSigma1PtTgl(); c(4,4)=GetSigma1Pt2();
982 c(0,0)+=t->GetSigmaY2();
983 c(1,0)+=t->GetSigmaZY(); c(1,1)+=t->GetSigmaZ2();
984 c(2,0)+=t->GetSigmaSnpY();c(2,1)+=t->GetSigmaSnpZ();c(2,2)+=t->GetSigmaSnp2();
985 c(3,0)+=t->GetSigmaTglY();c(3,1)+=t->GetSigmaTglZ();c(3,2)+=t->GetSigmaTglSnp();c(3,3)+=t->GetSigmaTgl2();
986 c(4,0)+=t->GetSigma1PtY();c(4,1)+=t->GetSigma1PtZ();c(4,2)+=t->GetSigma1PtSnp();c(4,3)+=t->GetSigma1PtTgl();c(4,4)+=t->GetSigma1Pt2();
988 c(0,2)=c(2,0); c(1,2)=c(2,1);
989 c(0,3)=c(3,0); c(1,3)=c(3,1); c(2,3)=c(3,2);
990 c(0,4)=c(4,0); c(1,4)=c(4,1); c(2,4)=c(4,2); c(3,4)=c(4,3);
993 if (!c.IsValid()) return kVeryBig;
999 GetSnp() - t->GetSnp(),
1000 GetTgl() - t->GetTgl(),
1001 GetSigned1Pt() - t->GetSigned1Pt()
1005 for (Int_t i = 0; i < 5; i++)
1006 for (Int_t j = 0; j < 5; j++) chi2 += res[i]*res[j]*c(i,j);
1011 Bool_t AliExternalTrackParam::
1012 PropagateTo(Double_t p[3],Double_t covyz[3],Double_t covxyz[3],Double_t bz) {
1013 //----------------------------------------------------------------
1014 // Propagate this track to the plane
1015 // the 3D space point "p" (with the covariance matrix "covyz" and "covxyz")
1017 // The magnetic field is "bz" (kG)
1019 // The track curvature and the change of the covariance matrix
1020 // of the track parameters are negleted !
1021 // (So the "step" should be small compared with 1/curvature)
1022 //----------------------------------------------------------------
1024 Double_t f=GetSnp();
1025 if (TMath::Abs(f) >= kAlmost1) return kFALSE;
1026 Double_t r=TMath::Sqrt((1.-f)*(1.+f));
1027 Double_t a=f/r, b=GetTgl()/r;
1029 Double_t s2=333.*333.; //something reasonably big (cm^2)
1032 tV(0,0)= s2; tV(0,1)= a*s2; tV(0,2)= b*s2;
1033 tV(1,0)=a*s2; tV(1,1)=a*a*s2; tV(1,2)=a*b*s2;
1034 tV(2,0)=b*s2; tV(2,1)=a*b*s2; tV(2,2)=b*b*s2;
1037 pV(0,0)=covxyz[0]; pV(0,1)=covxyz[1]; pV(0,2)=covxyz[2];
1038 pV(1,0)=covxyz[1]; pV(1,1)=covyz[0]; pV(1,2)=covyz[1];
1039 pV(2,0)=covxyz[2]; pV(2,1)=covyz[1]; pV(2,2)=covyz[2];
1041 TMatrixDSym tpV(tV);
1044 if (!tpV.IsValid()) return kFALSE;
1046 TMatrixDSym pW(3),tW(3);
1047 for (Int_t i=0; i<3; i++)
1048 for (Int_t j=0; j<3; j++) {
1050 for (Int_t k=0; k<3; k++) {
1051 pW(i,j) += tV(i,k)*tpV(k,j);
1052 tW(i,j) += pV(i,k)*tpV(k,j);
1056 Double_t t[3] = {GetX(), GetY(), GetZ()};
1059 for (Int_t i=0; i<3; i++) x += (tW(0,i)*t[i] + pW(0,i)*p[i]);
1060 Double_t crv=GetC(bz);
1061 if (TMath::Abs(b) < kAlmost0Field) crv=0.;
1063 if (TMath::Abs(f) >= kAlmost1) return kFALSE;
1067 for (Int_t i=0; i<3; i++) fP[0] += (tW(1,i)*t[i] + pW(1,i)*p[i]);
1069 for (Int_t i=0; i<3; i++) fP[1] += (tW(2,i)*t[i] + pW(2,i)*p[i]);
1074 Double_t *AliExternalTrackParam::GetResiduals(
1075 Double_t *p,Double_t *cov,Bool_t updated) const {
1076 //------------------------------------------------------------------
1077 // Returns the track residuals with the space point "p" having
1078 // the covariance matrix "cov".
1079 // If "updated" is kTRUE, the track parameters expected to be updated,
1080 // otherwise they must be predicted.
1081 //------------------------------------------------------------------
1082 static Double_t res[2];
1084 Double_t r00=cov[0], r01=cov[1], r11=cov[2];
1086 r00-=fC[0]; r01-=fC[1]; r11-=fC[2];
1088 r00+=fC[0]; r01+=fC[1]; r11+=fC[2];
1090 Double_t det=r00*r11 - r01*r01;
1092 if (TMath::Abs(det) < kAlmost0) return 0;
1094 Double_t tmp=r00; r00=r11/det; r11=tmp/det;
1096 if (r00 < 0.) return 0;
1097 if (r11 < 0.) return 0;
1099 Double_t dy = fP[0] - p[0];
1100 Double_t dz = fP[1] - p[1];
1102 res[0]=dy*TMath::Sqrt(r00);
1103 res[1]=dz*TMath::Sqrt(r11);
1108 Bool_t AliExternalTrackParam::Update(Double_t p[2], Double_t cov[3]) {
1109 //------------------------------------------------------------------
1110 // Update the track parameters with the space point "p" having
1111 // the covariance matrix "cov"
1112 //------------------------------------------------------------------
1113 Double_t &fP0=fP[0], &fP1=fP[1], &fP2=fP[2], &fP3=fP[3], &fP4=fP[4];
1116 &fC10=fC[1], &fC11=fC[2],
1117 &fC20=fC[3], &fC21=fC[4], &fC22=fC[5],
1118 &fC30=fC[6], &fC31=fC[7], &fC32=fC[8], &fC33=fC[9],
1119 &fC40=fC[10], &fC41=fC[11], &fC42=fC[12], &fC43=fC[13], &fC44=fC[14];
1121 Double_t r00=cov[0], r01=cov[1], r11=cov[2];
1122 r00+=fC00; r01+=fC10; r11+=fC11;
1123 Double_t det=r00*r11 - r01*r01;
1125 if (TMath::Abs(det) < kAlmost0) return kFALSE;
1128 Double_t tmp=r00; r00=r11/det; r11=tmp/det; r01=-r01/det;
1130 Double_t k00=fC00*r00+fC10*r01, k01=fC00*r01+fC10*r11;
1131 Double_t k10=fC10*r00+fC11*r01, k11=fC10*r01+fC11*r11;
1132 Double_t k20=fC20*r00+fC21*r01, k21=fC20*r01+fC21*r11;
1133 Double_t k30=fC30*r00+fC31*r01, k31=fC30*r01+fC31*r11;
1134 Double_t k40=fC40*r00+fC41*r01, k41=fC40*r01+fC41*r11;
1136 Double_t dy=p[0] - fP0, dz=p[1] - fP1;
1137 Double_t sf=fP2 + k20*dy + k21*dz;
1138 if (TMath::Abs(sf) > kAlmost1) return kFALSE;
1140 fP0 += k00*dy + k01*dz;
1141 fP1 += k10*dy + k11*dz;
1143 fP3 += k30*dy + k31*dz;
1144 fP4 += k40*dy + k41*dz;
1146 Double_t c01=fC10, c02=fC20, c03=fC30, c04=fC40;
1147 Double_t c12=fC21, c13=fC31, c14=fC41;
1149 fC00-=k00*fC00+k01*fC10; fC10-=k00*c01+k01*fC11;
1150 fC20-=k00*c02+k01*c12; fC30-=k00*c03+k01*c13;
1151 fC40-=k00*c04+k01*c14;
1153 fC11-=k10*c01+k11*fC11;
1154 fC21-=k10*c02+k11*c12; fC31-=k10*c03+k11*c13;
1155 fC41-=k10*c04+k11*c14;
1157 fC22-=k20*c02+k21*c12; fC32-=k20*c03+k21*c13;
1158 fC42-=k20*c04+k21*c14;
1160 fC33-=k30*c03+k31*c13;
1161 fC43-=k30*c04+k31*c14;
1163 fC44-=k40*c04+k41*c14;
1171 AliExternalTrackParam::GetHelixParameters(Double_t hlx[6], Double_t b) const {
1172 //--------------------------------------------------------------------
1173 // External track parameters -> helix parameters
1174 // "b" - magnetic field (kG)
1175 //--------------------------------------------------------------------
1176 Double_t cs=TMath::Cos(fAlpha), sn=TMath::Sin(fAlpha);
1178 hlx[0]=fP[0]; hlx[1]=fP[1]; hlx[2]=fP[2]; hlx[3]=fP[3];
1180 hlx[5]=fX*cs - hlx[0]*sn; // x0
1181 hlx[0]=fX*sn + hlx[0]*cs; // y0
1183 hlx[2]=TMath::ASin(hlx[2]) + fAlpha; // phi0
1185 hlx[4]=GetC(b); // C
1189 static void Evaluate(const Double_t *h, Double_t t,
1190 Double_t r[3], //radius vector
1191 Double_t g[3], //first defivatives
1192 Double_t gg[3]) //second derivatives
1194 //--------------------------------------------------------------------
1195 // Calculate position of a point on a track and some derivatives
1196 //--------------------------------------------------------------------
1197 Double_t phase=h[4]*t+h[2];
1198 Double_t sn=TMath::Sin(phase), cs=TMath::Cos(phase);
1202 if (TMath::Abs(h[4])>kAlmost0) {
1203 r[0] += (sn - h[6])/h[4];
1204 r[1] -= (cs - h[7])/h[4];
1206 r[2] = h[1] + h[3]*t;
1208 g[0] = cs; g[1]=sn; g[2]=h[3];
1210 gg[0]=-h[4]*sn; gg[1]=h[4]*cs; gg[2]=0.;
1213 Double_t AliExternalTrackParam::GetDCA(const AliExternalTrackParam *p,
1214 Double_t b, Double_t &xthis, Double_t &xp) const {
1215 //------------------------------------------------------------
1216 // Returns the (weighed !) distance of closest approach between
1217 // this track and the track "p".
1218 // Other returned values:
1219 // xthis, xt - coordinates of tracks' reference planes at the DCA
1220 //-----------------------------------------------------------
1221 Double_t dy2=GetSigmaY2() + p->GetSigmaY2();
1222 Double_t dz2=GetSigmaZ2() + p->GetSigmaZ2();
1225 Double_t p1[8]; GetHelixParameters(p1,b);
1226 p1[6]=TMath::Sin(p1[2]); p1[7]=TMath::Cos(p1[2]);
1227 Double_t p2[8]; p->GetHelixParameters(p2,b);
1228 p2[6]=TMath::Sin(p2[2]); p2[7]=TMath::Cos(p2[2]);
1231 Double_t r1[3],g1[3],gg1[3]; Double_t t1=0.;
1232 Evaluate(p1,t1,r1,g1,gg1);
1233 Double_t r2[3],g2[3],gg2[3]; Double_t t2=0.;
1234 Evaluate(p2,t2,r2,g2,gg2);
1236 Double_t dx=r2[0]-r1[0], dy=r2[1]-r1[1], dz=r2[2]-r1[2];
1237 Double_t dm=dx*dx/dx2 + dy*dy/dy2 + dz*dz/dz2;
1241 Double_t gt1=-(dx*g1[0]/dx2 + dy*g1[1]/dy2 + dz*g1[2]/dz2);
1242 Double_t gt2=+(dx*g2[0]/dx2 + dy*g2[1]/dy2 + dz*g2[2]/dz2);
1243 Double_t h11=(g1[0]*g1[0] - dx*gg1[0])/dx2 +
1244 (g1[1]*g1[1] - dy*gg1[1])/dy2 +
1245 (g1[2]*g1[2] - dz*gg1[2])/dz2;
1246 Double_t h22=(g2[0]*g2[0] + dx*gg2[0])/dx2 +
1247 (g2[1]*g2[1] + dy*gg2[1])/dy2 +
1248 (g2[2]*g2[2] + dz*gg2[2])/dz2;
1249 Double_t h12=-(g1[0]*g2[0]/dx2 + g1[1]*g2[1]/dy2 + g1[2]*g2[2]/dz2);
1251 Double_t det=h11*h22-h12*h12;
1254 if (TMath::Abs(det)<1.e-33) {
1255 //(quasi)singular Hessian
1258 dt1=-(gt1*h22 - gt2*h12)/det;
1259 dt2=-(h11*gt2 - h12*gt1)/det;
1262 if ((dt1*gt1+dt2*gt2)>0) {dt1=-dt1; dt2=-dt2;}
1264 //check delta(phase1) ?
1265 //check delta(phase2) ?
1267 if (TMath::Abs(dt1)/(TMath::Abs(t1)+1.e-3) < 1.e-4)
1268 if (TMath::Abs(dt2)/(TMath::Abs(t2)+1.e-3) < 1.e-4) {
1269 if ((gt1*gt1+gt2*gt2) > 1.e-4/dy2/dy2)
1270 AliDebug(1," stopped at not a stationary point !");
1271 Double_t lmb=h11+h22; lmb=lmb-TMath::Sqrt(lmb*lmb-4*det);
1273 AliDebug(1," stopped at not a minimum !");
1278 for (Int_t div=1 ; ; div*=2) {
1279 Evaluate(p1,t1+dt1,r1,g1,gg1);
1280 Evaluate(p2,t2+dt2,r2,g2,gg2);
1281 dx=r2[0]-r1[0]; dy=r2[1]-r1[1]; dz=r2[2]-r1[2];
1282 dd=dx*dx/dx2 + dy*dy/dy2 + dz*dz/dz2;
1286 AliDebug(1," overshoot !"); break;
1296 if (max<=0) AliDebug(1," too many iterations !");
1298 Double_t cs=TMath::Cos(GetAlpha());
1299 Double_t sn=TMath::Sin(GetAlpha());
1300 xthis=r1[0]*cs + r1[1]*sn;
1302 cs=TMath::Cos(p->GetAlpha());
1303 sn=TMath::Sin(p->GetAlpha());
1304 xp=r2[0]*cs + r2[1]*sn;
1306 return TMath::Sqrt(dm*TMath::Sqrt(dy2*dz2));
1309 Double_t AliExternalTrackParam::
1310 PropagateToDCA(AliExternalTrackParam *p, Double_t b) {
1311 //--------------------------------------------------------------
1312 // Propagates this track and the argument track to the position of the
1313 // distance of closest approach.
1314 // Returns the (weighed !) distance of closest approach.
1315 //--------------------------------------------------------------
1317 Double_t dca=GetDCA(p,b,xthis,xp);
1319 if (!PropagateTo(xthis,b)) {
1320 //AliWarning(" propagation failed !");
1324 if (!p->PropagateTo(xp,b)) {
1325 //AliWarning(" propagation failed !";
1333 Bool_t AliExternalTrackParam::PropagateToDCA(const AliVVertex *vtx,
1334 Double_t b, Double_t maxd, Double_t dz[2], Double_t covar[3]) {
1336 // Propagate this track to the DCA to vertex "vtx",
1337 // if the (rough) transverse impact parameter is not bigger then "maxd".
1338 // Magnetic field is "b" (kG).
1340 // a) The track gets extapolated to the DCA to the vertex.
1341 // b) The impact parameters and their covariance matrix are calculated.
1343 // In the case of success, the returned value is kTRUE
1344 // (otherwise, it's kFALSE)
1346 Double_t alpha=GetAlpha();
1347 Double_t sn=TMath::Sin(alpha), cs=TMath::Cos(alpha);
1348 Double_t x=GetX(), y=GetParameter()[0], snp=GetParameter()[2];
1349 Double_t xv= vtx->GetX()*cs + vtx->GetY()*sn;
1350 Double_t yv=-vtx->GetX()*sn + vtx->GetY()*cs, zv=vtx->GetZ();
1353 //Estimate the impact parameter neglecting the track curvature
1354 Double_t d=TMath::Abs(x*snp - y*TMath::Sqrt((1.-snp)*(1.+snp)));
1355 if (d > maxd) return kFALSE;
1357 //Propagate to the DCA
1358 Double_t crv=GetC(b);
1359 if (TMath::Abs(b) < kAlmost0Field) crv=0.;
1361 Double_t tgfv=-(crv*x - snp)/(crv*y + TMath::Sqrt((1.-snp)*(1.+snp)));
1362 sn=tgfv/TMath::Sqrt(1.+ tgfv*tgfv); cs=TMath::Sqrt((1.-sn)*(1.+sn));
1363 if (TMath::Abs(tgfv)>0.) cs = sn/tgfv;
1367 yv=-xv*sn + yv*cs; xv=x;
1369 if (!Propagate(alpha+TMath::ASin(sn),xv,b)) return kFALSE;
1371 if (dz==0) return kTRUE;
1372 dz[0] = GetParameter()[0] - yv;
1373 dz[1] = GetParameter()[1] - zv;
1375 if (covar==0) return kTRUE;
1376 Double_t cov[6]; vtx->GetCovarianceMatrix(cov);
1378 //***** Improvements by A.Dainese
1379 alpha=GetAlpha(); sn=TMath::Sin(alpha); cs=TMath::Cos(alpha);
1380 Double_t s2ylocvtx = cov[0]*sn*sn + cov[2]*cs*cs - 2.*cov[1]*cs*sn;
1381 covar[0] = GetCovariance()[0] + s2ylocvtx; // neglecting correlations
1382 covar[1] = GetCovariance()[1]; // between (x,y) and z
1383 covar[2] = GetCovariance()[2] + cov[5]; // in vertex's covariance matrix
1389 Bool_t AliExternalTrackParam::PropagateToDCABxByBz(const AliVVertex *vtx,
1390 Double_t b[3], Double_t maxd, Double_t dz[2], Double_t covar[3]) {
1392 // Propagate this track to the DCA to vertex "vtx",
1393 // if the (rough) transverse impact parameter is not bigger then "maxd".
1395 // This function takes into account all three components of the magnetic
1396 // field given by the b[3] arument (kG)
1398 // a) The track gets extapolated to the DCA to the vertex.
1399 // b) The impact parameters and their covariance matrix are calculated.
1401 // In the case of success, the returned value is kTRUE
1402 // (otherwise, it's kFALSE)
1404 Double_t alpha=GetAlpha();
1405 Double_t sn=TMath::Sin(alpha), cs=TMath::Cos(alpha);
1406 Double_t x=GetX(), y=GetParameter()[0], snp=GetParameter()[2];
1407 Double_t xv= vtx->GetX()*cs + vtx->GetY()*sn;
1408 Double_t yv=-vtx->GetX()*sn + vtx->GetY()*cs, zv=vtx->GetZ();
1411 //Estimate the impact parameter neglecting the track curvature
1412 Double_t d=TMath::Abs(x*snp - y*TMath::Sqrt((1.-snp)*(1.+snp)));
1413 if (d > maxd) return kFALSE;
1415 //Propagate to the DCA
1416 Double_t crv=GetC(b[2]);
1417 if (TMath::Abs(b[2]) < kAlmost0Field) crv=0.;
1419 Double_t tgfv=-(crv*x - snp)/(crv*y + TMath::Sqrt((1.-snp)*(1.+snp)));
1420 sn=tgfv/TMath::Sqrt(1.+ tgfv*tgfv); cs=TMath::Sqrt((1.-sn)*(1.+sn));
1421 if (TMath::Abs(tgfv)>0.) cs = sn/tgfv;
1425 yv=-xv*sn + yv*cs; xv=x;
1427 if (!PropagateBxByBz(alpha+TMath::ASin(sn),xv,b)) return kFALSE;
1429 if (dz==0) return kTRUE;
1430 dz[0] = GetParameter()[0] - yv;
1431 dz[1] = GetParameter()[1] - zv;
1433 if (covar==0) return kTRUE;
1434 Double_t cov[6]; vtx->GetCovarianceMatrix(cov);
1436 //***** Improvements by A.Dainese
1437 alpha=GetAlpha(); sn=TMath::Sin(alpha); cs=TMath::Cos(alpha);
1438 Double_t s2ylocvtx = cov[0]*sn*sn + cov[2]*cs*cs - 2.*cov[1]*cs*sn;
1439 covar[0] = GetCovariance()[0] + s2ylocvtx; // neglecting correlations
1440 covar[1] = GetCovariance()[1]; // between (x,y) and z
1441 covar[2] = GetCovariance()[2] + cov[5]; // in vertex's covariance matrix
1447 void AliExternalTrackParam::GetDirection(Double_t d[3]) const {
1448 //----------------------------------------------------------------
1449 // This function returns a unit vector along the track direction
1450 // in the global coordinate system.
1451 //----------------------------------------------------------------
1452 Double_t cs=TMath::Cos(fAlpha), sn=TMath::Sin(fAlpha);
1454 Double_t csp =TMath::Sqrt((1.-snp)*(1.+snp));
1455 Double_t norm=TMath::Sqrt(1.+ fP[3]*fP[3]);
1456 d[0]=(csp*cs - snp*sn)/norm;
1457 d[1]=(snp*cs + csp*sn)/norm;
1461 Bool_t AliExternalTrackParam::GetPxPyPz(Double_t p[3]) const {
1462 //---------------------------------------------------------------------
1463 // This function returns the global track momentum components
1464 // Results for (nearly) straight tracks are meaningless !
1465 //---------------------------------------------------------------------
1466 p[0]=fP[4]; p[1]=fP[2]; p[2]=fP[3];
1467 return Local2GlobalMomentum(p,fAlpha);
1470 Double_t AliExternalTrackParam::Px() const {
1471 //---------------------------------------------------------------------
1472 // Returns x-component of momentum
1473 // Result for (nearly) straight tracks is meaningless !
1474 //---------------------------------------------------------------------
1476 Double_t p[3]={kVeryBig,kVeryBig,kVeryBig};
1482 Double_t AliExternalTrackParam::Py() const {
1483 //---------------------------------------------------------------------
1484 // Returns y-component of momentum
1485 // Result for (nearly) straight tracks is meaningless !
1486 //---------------------------------------------------------------------
1488 Double_t p[3]={kVeryBig,kVeryBig,kVeryBig};
1494 Double_t AliExternalTrackParam::Xv() const {
1495 //---------------------------------------------------------------------
1496 // Returns x-component of first track point
1497 //---------------------------------------------------------------------
1499 Double_t r[3]={0.,0.,0.};
1505 Double_t AliExternalTrackParam::Yv() const {
1506 //---------------------------------------------------------------------
1507 // Returns y-component of first track point
1508 //---------------------------------------------------------------------
1510 Double_t r[3]={0.,0.,0.};
1516 Double_t AliExternalTrackParam::Theta() const {
1517 // return theta angle of momentum
1519 return 0.5*TMath::Pi() - TMath::ATan(fP[3]);
1522 Double_t AliExternalTrackParam::Phi() const {
1523 //---------------------------------------------------------------------
1524 // Returns the azimuthal angle of momentum
1526 //---------------------------------------------------------------------
1528 Double_t phi=TMath::ASin(fP[2]) + fAlpha;
1529 if (phi<0.) phi+=2.*TMath::Pi();
1530 else if (phi>=2.*TMath::Pi()) phi-=2.*TMath::Pi();
1535 Double_t AliExternalTrackParam::M() const {
1536 // return particle mass
1538 // No mass information available so far.
1539 // Redifine in derived class!
1544 Double_t AliExternalTrackParam::E() const {
1545 // return particle energy
1547 // No PID information available so far.
1548 // Redifine in derived class!
1553 Double_t AliExternalTrackParam::Eta() const {
1554 // return pseudorapidity
1556 return -TMath::Log(TMath::Tan(0.5 * Theta()));
1559 Double_t AliExternalTrackParam::Y() const {
1562 // No PID information available so far.
1563 // Redifine in derived class!
1568 Bool_t AliExternalTrackParam::GetXYZ(Double_t *r) const {
1569 //---------------------------------------------------------------------
1570 // This function returns the global track position
1571 //---------------------------------------------------------------------
1572 r[0]=fX; r[1]=fP[0]; r[2]=fP[1];
1573 return Local2GlobalPosition(r,fAlpha);
1576 Bool_t AliExternalTrackParam::GetCovarianceXYZPxPyPz(Double_t cv[21]) const {
1577 //---------------------------------------------------------------------
1578 // This function returns the global covariance matrix of the track params
1580 // Cov(x,x) ... : cv[0]
1581 // Cov(y,x) ... : cv[1] cv[2]
1582 // Cov(z,x) ... : cv[3] cv[4] cv[5]
1583 // Cov(px,x)... : cv[6] cv[7] cv[8] cv[9]
1584 // Cov(py,x)... : cv[10] cv[11] cv[12] cv[13] cv[14]
1585 // Cov(pz,x)... : cv[15] cv[16] cv[17] cv[18] cv[19] cv[20]
1587 // Results for (nearly) straight tracks are meaningless !
1588 //---------------------------------------------------------------------
1589 if (TMath::Abs(fP[4])<=kAlmost0) {
1590 for (Int_t i=0; i<21; i++) cv[i]=0.;
1593 if (TMath::Abs(fP[2]) > kAlmost1) {
1594 for (Int_t i=0; i<21; i++) cv[i]=0.;
1597 Double_t pt=1./TMath::Abs(fP[4]);
1598 Double_t cs=TMath::Cos(fAlpha), sn=TMath::Sin(fAlpha);
1599 Double_t r=TMath::Sqrt((1.-fP[2])*(1.+fP[2]));
1601 Double_t m00=-sn, m10=cs;
1602 Double_t m23=-pt*(sn + fP[2]*cs/r), m43=-pt*pt*(r*cs - fP[2]*sn);
1603 Double_t m24= pt*(cs - fP[2]*sn/r), m44=-pt*pt*(r*sn + fP[2]*cs);
1604 Double_t m35=pt, m45=-pt*pt*fP[3];
1610 cv[0 ] = fC[0]*m00*m00;
1611 cv[1 ] = fC[0]*m00*m10;
1612 cv[2 ] = fC[0]*m10*m10;
1616 cv[6 ] = m00*(fC[3]*m23 + fC[10]*m43);
1617 cv[7 ] = m10*(fC[3]*m23 + fC[10]*m43);
1618 cv[8 ] = fC[4]*m23 + fC[11]*m43;
1619 cv[9 ] = m23*(fC[5]*m23 + fC[12]*m43) + m43*(fC[12]*m23 + fC[14]*m43);
1620 cv[10] = m00*(fC[3]*m24 + fC[10]*m44);
1621 cv[11] = m10*(fC[3]*m24 + fC[10]*m44);
1622 cv[12] = fC[4]*m24 + fC[11]*m44;
1623 cv[13] = m23*(fC[5]*m24 + fC[12]*m44) + m43*(fC[12]*m24 + fC[14]*m44);
1624 cv[14] = m24*(fC[5]*m24 + fC[12]*m44) + m44*(fC[12]*m24 + fC[14]*m44);
1625 cv[15] = m00*(fC[6]*m35 + fC[10]*m45);
1626 cv[16] = m10*(fC[6]*m35 + fC[10]*m45);
1627 cv[17] = fC[7]*m35 + fC[11]*m45;
1628 cv[18] = m23*(fC[8]*m35 + fC[12]*m45) + m43*(fC[13]*m35 + fC[14]*m45);
1629 cv[19] = m24*(fC[8]*m35 + fC[12]*m45) + m44*(fC[13]*m35 + fC[14]*m45);
1630 cv[20] = m35*(fC[9]*m35 + fC[13]*m45) + m45*(fC[13]*m35 + fC[14]*m45);
1637 AliExternalTrackParam::GetPxPyPzAt(Double_t x, Double_t b, Double_t *p) const {
1638 //---------------------------------------------------------------------
1639 // This function returns the global track momentum extrapolated to
1640 // the radial position "x" (cm) in the magnetic field "b" (kG)
1641 //---------------------------------------------------------------------
1643 p[1]=fP[2]+(x-fX)*GetC(b);
1645 return Local2GlobalMomentum(p,fAlpha);
1649 AliExternalTrackParam::GetYAt(Double_t x, Double_t b, Double_t &y) const {
1650 //---------------------------------------------------------------------
1651 // This function returns the local Y-coordinate of the intersection
1652 // point between this track and the reference plane "x" (cm).
1653 // Magnetic field "b" (kG)
1654 //---------------------------------------------------------------------
1656 if(TMath::Abs(dx)<=kAlmost0) {y=fP[0]; return kTRUE;}
1658 Double_t f1=fP[2], f2=f1 + dx*GetC(b);
1660 if (TMath::Abs(f1) >= kAlmost1) return kFALSE;
1661 if (TMath::Abs(f2) >= kAlmost1) return kFALSE;
1663 Double_t r1=TMath::Sqrt((1.-f1)*(1.+f1)), r2=TMath::Sqrt((1.-f2)*(1.+f2));
1664 y = fP[0] + dx*(f1+f2)/(r1+r2);
1669 AliExternalTrackParam::GetZAt(Double_t x, Double_t b, Double_t &z) const {
1670 //---------------------------------------------------------------------
1671 // This function returns the local Z-coordinate of the intersection
1672 // point between this track and the reference plane "x" (cm).
1673 // Magnetic field "b" (kG)
1674 //---------------------------------------------------------------------
1676 if(TMath::Abs(dx)<=kAlmost0) {z=fP[1]; return kTRUE;}
1678 Double_t f1=fP[2], f2=f1 + dx*GetC(b);
1680 if (TMath::Abs(f1) >= kAlmost1) return kFALSE;
1681 if (TMath::Abs(f2) >= kAlmost1) return kFALSE;
1683 Double_t r1=sqrt((1.-f1)*(1.+f1)), r2=sqrt((1.-f2)*(1.+f2));
1684 z = fP[1] + dx*(r2 + f2*(f1+f2)/(r1+r2))*fP[3]; // Many thanks to P.Hristov !
1689 AliExternalTrackParam::GetXYZAt(Double_t x, Double_t b, Double_t *r) const {
1690 //---------------------------------------------------------------------
1691 // This function returns the global track position extrapolated to
1692 // the radial position "x" (cm) in the magnetic field "b" (kG)
1693 //---------------------------------------------------------------------
1695 if(TMath::Abs(dx)<=kAlmost0) return GetXYZ(r);
1697 Double_t f1=fP[2], f2=f1 + dx*GetC(b);
1699 if (TMath::Abs(f1) >= kAlmost1) return kFALSE;
1700 if (TMath::Abs(f2) >= kAlmost1) return kFALSE;
1702 Double_t r1=TMath::Sqrt((1.-f1)*(1.+f1)), r2=TMath::Sqrt((1.-f2)*(1.+f2));
1704 r[1] = fP[0] + dx*(f1+f2)/(r1+r2);
1705 r[2] = fP[1] + dx*(r2 + f2*(f1+f2)/(r1+r2))*fP[3];//Thanks to Andrea & Peter
1707 return Local2GlobalPosition(r,fAlpha);
1710 //_____________________________________________________________________________
1711 void AliExternalTrackParam::Print(Option_t* /*option*/) const
1713 // print the parameters and the covariance matrix
1715 printf("AliExternalTrackParam: x = %-12g alpha = %-12g\n", fX, fAlpha);
1716 printf(" parameters: %12g %12g %12g %12g %12g\n",
1717 fP[0], fP[1], fP[2], fP[3], fP[4]);
1718 printf(" covariance: %12g\n", fC[0]);
1719 printf(" %12g %12g\n", fC[1], fC[2]);
1720 printf(" %12g %12g %12g\n", fC[3], fC[4], fC[5]);
1721 printf(" %12g %12g %12g %12g\n",
1722 fC[6], fC[7], fC[8], fC[9]);
1723 printf(" %12g %12g %12g %12g %12g\n",
1724 fC[10], fC[11], fC[12], fC[13], fC[14]);
1727 Double_t AliExternalTrackParam::GetSnpAt(Double_t x,Double_t b) const {
1729 // Get sinus at given x
1731 Double_t crv=GetC(b);
1732 if (TMath::Abs(b) < kAlmost0Field) crv=0.;
1734 Double_t res = fP[2]+dx*crv;
1738 Bool_t AliExternalTrackParam::GetDistance(AliExternalTrackParam *param2, Double_t x, Double_t dist[3], Double_t bz){
1739 //------------------------------------------------------------------------
1740 // Get the distance between two tracks at the local position x
1741 // working in the local frame of this track.
1742 // Origin : Marian.Ivanov@cern.ch
1743 //-----------------------------------------------------------------------
1747 if (!GetYAt(x,bz,xyz[1])) return kFALSE;
1748 if (!GetZAt(x,bz,xyz[2])) return kFALSE;
1751 if (TMath::Abs(GetAlpha()-param2->GetAlpha())<kAlmost0){
1753 if (!param2->GetYAt(x,bz,xyz2[1])) return kFALSE;
1754 if (!param2->GetZAt(x,bz,xyz2[2])) return kFALSE;
1758 Double_t dfi = param2->GetAlpha()-GetAlpha();
1759 Double_t ca = TMath::Cos(dfi), sa = TMath::Sin(dfi);
1760 xyz2[0] = xyz[0]*ca+xyz[1]*sa;
1761 xyz2[1] = -xyz[0]*sa+xyz[1]*ca;
1764 if (!param2->GetYAt(xyz2[0],bz,xyz1[1])) return kFALSE;
1765 if (!param2->GetZAt(xyz2[0],bz,xyz1[2])) return kFALSE;
1767 xyz2[0] = xyz1[0]*ca-xyz1[1]*sa;
1768 xyz2[1] = +xyz1[0]*sa+xyz1[1]*ca;
1771 dist[0] = xyz[0]-xyz2[0];
1772 dist[1] = xyz[1]-xyz2[1];
1773 dist[2] = xyz[2]-xyz2[2];
1780 // Draw functionality.
1781 // Origin: Marian Ivanov, Marian.Ivanov@cern.ch
1784 void AliExternalTrackParam::DrawTrack(Float_t magf, Float_t minR, Float_t maxR, Float_t stepR){
1788 if (minR>maxR) return ;
1789 if (stepR<=0) return ;
1790 Int_t npoints = TMath::Nint((maxR-minR)/stepR)+1;
1791 if (npoints<1) return;
1792 TPolyMarker3D *polymarker = new TPolyMarker3D(npoints);
1793 FillPolymarker(polymarker, magf,minR,maxR,stepR);
1798 void AliExternalTrackParam::FillPolymarker(TPolyMarker3D *pol, Float_t magF, Float_t minR, Float_t maxR, Float_t stepR){
1800 // Fill points in the polymarker
1803 for (Double_t r=minR; r<maxR; r+=stepR){
1805 GetXYZAt(r,magF,point);
1806 pol->SetPoint(counter,point[0],point[1], point[2]);
1807 printf("xyz\t%f\t%f\t%f\n",point[0], point[1],point[2]);
1812 Int_t AliExternalTrackParam::GetIndex(Int_t i, Int_t j) const {
1814 Int_t min = TMath::Min(i,j);
1815 Int_t max = TMath::Max(i,j);
1817 return min+(max+1)*max/2;
1821 void AliExternalTrackParam::g3helx3(Double_t qfield,
1824 /******************************************************************
1826 * GEANT3 tracking routine in a constant field oriented *
1828 * Tracking is performed with a conventional *
1829 * helix step method *
1831 * Authors R.Brun, M.Hansroul ********* *
1832 * Rewritten V.Perevoztchikov *
1834 * Rewritten in C++ by I.Belikov *
1836 * qfield (kG) - particle charge times magnetic field *
1837 * step (cm) - step length along the helix *
1838 * vect[7](cm,GeV/c) - input/output x, y, z, px/p, py/p ,pz/p, p *
1840 ******************************************************************/
1841 const Int_t ix=0, iy=1, iz=2, ipx=3, ipy=4, ipz=5, ipp=6;
1842 const Double_t kOvSqSix=TMath::Sqrt(1./6.);
1844 Double_t cosx=vect[ipx], cosy=vect[ipy], cosz=vect[ipz];
1846 Double_t rho = qfield*kB2C/vect[ipp];
1847 Double_t tet = rho*step;
1849 Double_t tsint, sintt, sint, cos1t;
1850 if (TMath::Abs(tet) > 0.03) {
1851 sint = TMath::Sin(tet);
1853 tsint = (tet - sint)/tet;
1854 Double_t t=TMath::Sin(0.5*tet);
1858 sintt = (1.-tet*kOvSqSix)*(1.+tet*kOvSqSix); // 1.- tsint;
1863 Double_t f1 = step*sintt;
1864 Double_t f2 = step*cos1t;
1865 Double_t f3 = step*tsint*cosz;
1866 Double_t f4 = -tet*cos1t;
1869 vect[ix] += f1*cosx - f2*cosy;
1870 vect[iy] += f1*cosy + f2*cosx;
1871 vect[iz] += f1*cosz + f3;
1873 vect[ipx] += f4*cosx - f5*cosy;
1874 vect[ipy] += f4*cosy + f5*cosx;
1878 Bool_t AliExternalTrackParam::PropagateToBxByBz(Double_t xk, const Double_t b[3]) {
1879 //----------------------------------------------------------------
1880 // Extrapolate this track to the plane X=xk in the field b[].
1882 // X [cm] is in the "tracking coordinate system" of this track.
1883 // b[]={Bx,By,Bz} [kG] is in the Global coordidate system.
1884 //----------------------------------------------------------------
1887 if (TMath::Abs(dx)<=kAlmost0) return kTRUE;
1888 if (TMath::Abs(fP[4])<=kAlmost0) return kFALSE;
1889 // Do not propagate tracks outside the ALICE detector
1890 if (TMath::Abs(dx)>1e5 ||
1891 TMath::Abs(GetY())>1e5 ||
1892 TMath::Abs(GetZ())>1e5) {
1893 AliWarning(Form("Anomalous track, target X:%f",xk));
1898 Double_t crv=GetC(b[2]);
1899 if (TMath::Abs(b[2]) < kAlmost0Field) crv=0.;
1901 Double_t x2r = crv*dx;
1902 Double_t f1=fP[2], f2=f1 + x2r;
1903 if (TMath::Abs(f1) >= kAlmost1) return kFALSE;
1904 if (TMath::Abs(f2) >= kAlmost1) return kFALSE;
1907 // Estimate the covariance matrix
1908 Double_t &fP3=fP[3], &fP4=fP[4];
1911 &fC10=fC[1], &fC11=fC[2],
1912 &fC20=fC[3], &fC21=fC[4], &fC22=fC[5],
1913 &fC30=fC[6], &fC31=fC[7], &fC32=fC[8], &fC33=fC[9],
1914 &fC40=fC[10], &fC41=fC[11], &fC42=fC[12], &fC43=fC[13], &fC44=fC[14];
1916 Double_t r1=TMath::Sqrt((1.-f1)*(1.+f1)), r2=TMath::Sqrt((1.-f2)*(1.+f2));
1919 Double_t f02= dx/(r1*r1*r1); Double_t cc=crv/fP4;
1920 Double_t f04=0.5*dx*dx/(r1*r1*r1); f04*=cc;
1921 Double_t f12= dx*fP3*f1/(r1*r1*r1);
1922 Double_t f14=0.5*dx*dx*fP3*f1/(r1*r1*r1); f14*=cc;
1923 Double_t f13= dx/r1;
1924 Double_t f24= dx; f24*=cc;
1927 Double_t b00=f02*fC20 + f04*fC40, b01=f12*fC20 + f14*fC40 + f13*fC30;
1928 Double_t b02=f24*fC40;
1929 Double_t b10=f02*fC21 + f04*fC41, b11=f12*fC21 + f14*fC41 + f13*fC31;
1930 Double_t b12=f24*fC41;
1931 Double_t b20=f02*fC22 + f04*fC42, b21=f12*fC22 + f14*fC42 + f13*fC32;
1932 Double_t b22=f24*fC42;
1933 Double_t b40=f02*fC42 + f04*fC44, b41=f12*fC42 + f14*fC44 + f13*fC43;
1934 Double_t b42=f24*fC44;
1935 Double_t b30=f02*fC32 + f04*fC43, b31=f12*fC32 + f14*fC43 + f13*fC33;
1936 Double_t b32=f24*fC43;
1939 Double_t a00=f02*b20+f04*b40,a01=f02*b21+f04*b41,a02=f02*b22+f04*b42;
1940 Double_t a11=f12*b21+f14*b41+f13*b31,a12=f12*b22+f14*b42+f13*b32;
1941 Double_t a22=f24*b42;
1943 //F*C*Ft = C + (b + bt + a)
1944 fC00 += b00 + b00 + a00;
1945 fC10 += b10 + b01 + a01;
1946 fC20 += b20 + b02 + a02;
1949 fC11 += b11 + b11 + a11;
1950 fC21 += b21 + b12 + a12;
1953 fC22 += b22 + b22 + a22;
1959 // Appoximate step length
1960 double dy2dx = (f1+f2)/(r1+r2);
1961 Double_t step = (TMath::Abs(x2r)<0.05) ? dx*TMath::Abs(r2 + f2*dy2dx) // chord
1962 : 2.*TMath::ASin(0.5*dx*TMath::Sqrt(1.+dy2dx*dy2dx)*crv)/crv; // arc
1963 step *= TMath::Sqrt(1.+ GetTgl()*GetTgl());
1965 // Get the track's (x,y,z) and (px,py,pz) in the Global System
1966 Double_t r[3]; GetXYZ(r);
1967 Double_t p[3]; GetPxPyPz(p);
1974 // Rotate to the system where Bx=By=0.
1975 Double_t bt=TMath::Sqrt(b[0]*b[0] + b[1]*b[1]);
1976 Double_t cosphi=1., sinphi=0.;
1977 if (bt > kAlmost0) {cosphi=b[0]/bt; sinphi=b[1]/bt;}
1978 Double_t bb=TMath::Sqrt(b[0]*b[0] + b[1]*b[1] + b[2]*b[2]);
1979 Double_t costet=1., sintet=0.;
1980 if (bb > kAlmost0) {costet=b[2]/bb; sintet=bt/bb;}
1983 vect[0] = costet*cosphi*r[0] + costet*sinphi*r[1] - sintet*r[2];
1984 vect[1] = -sinphi*r[0] + cosphi*r[1];
1985 vect[2] = sintet*cosphi*r[0] + sintet*sinphi*r[1] + costet*r[2];
1987 vect[3] = costet*cosphi*p[0] + costet*sinphi*p[1] - sintet*p[2];
1988 vect[4] = -sinphi*p[0] + cosphi*p[1];
1989 vect[5] = sintet*cosphi*p[0] + sintet*sinphi*p[1] + costet*p[2];
1994 // Do the helix step
1995 g3helx3(GetSign()*bb,step,vect);
1998 // Rotate back to the Global System
1999 r[0] = cosphi*costet*vect[0] - sinphi*vect[1] + cosphi*sintet*vect[2];
2000 r[1] = sinphi*costet*vect[0] + cosphi*vect[1] + sinphi*sintet*vect[2];
2001 r[2] = -sintet*vect[0] + costet*vect[2];
2003 p[0] = cosphi*costet*vect[3] - sinphi*vect[4] + cosphi*sintet*vect[5];
2004 p[1] = sinphi*costet*vect[3] + cosphi*vect[4] + sinphi*sintet*vect[5];
2005 p[2] = -sintet*vect[3] + costet*vect[5];
2008 // Rotate back to the Tracking System
2009 Double_t cosalp = TMath::Cos(fAlpha);
2010 Double_t sinalp =-TMath::Sin(fAlpha);
2013 t = cosalp*r[0] - sinalp*r[1];
2014 r[1] = sinalp*r[0] + cosalp*r[1];
2017 t = cosalp*p[0] - sinalp*p[1];
2018 p[1] = sinalp*p[0] + cosalp*p[1];
2022 // Do the final correcting step to the target plane (linear approximation)
2023 Double_t x=r[0], y=r[1], z=r[2];
2024 if (TMath::Abs(dx) > kAlmost0) {
2025 if (TMath::Abs(p[0]) < kAlmost0) return kFALSE;
2033 // Calculate the track parameters
2034 t=TMath::Sqrt(p[0]*p[0] + p[1]*p[1]);
2040 fP[4] = GetSign()/(t*pp);
2045 Bool_t AliExternalTrackParam::Translate(Double_t *vTrasl,Double_t *covV){
2047 //Translation: in the event mixing, the tracks can be shifted
2048 //of the difference among primary vertices (vTrasl) and
2049 //the covariance matrix is changed accordingly
2050 //(covV = covariance of the primary vertex).
2051 //Origin: "Romita, Rossella" <R.Romita@gsi.de>
2053 TVector3 translation;
2054 // vTrasl coordinates in the local system
2055 translation.SetXYZ(vTrasl[0],vTrasl[1],vTrasl[2]);
2056 translation.RotateZ(-fAlpha);
2057 translation.GetXYZ(vTrasl);
2059 //compute the new x,y,z of the track
2060 Double_t newX=fX-vTrasl[0];
2061 Double_t newY=fP[0]-vTrasl[1];
2062 Double_t newZ=fP[1]-vTrasl[2];
2064 //define the new parameters
2065 Double_t newParam[5];
2072 // recompute the covariance matrix:
2073 // 1. covV in the local system
2074 Double_t cosRot=TMath::Cos(fAlpha), sinRot=TMath::Sin(fAlpha);
2095 if(uUi.Determinant() <= 0.) {return kFALSE;}
2096 TMatrixD uUiQi(uUi,TMatrixD::kMult,qQi);
2097 TMatrixD m(qQi,TMatrixD::kTransposeMult,uUiQi);
2099 //2. compute the new covariance matrix of the track
2100 Double_t sigmaXX=m(0,0);
2101 Double_t sigmaXZ=m(2,0);
2102 Double_t sigmaXY=m(1,0);
2103 Double_t sigmaYY=GetSigmaY2()+m(1,1);
2104 Double_t sigmaYZ=fC[1]+m(1,2);
2105 Double_t sigmaZZ=fC[2]+m(2,2);
2106 Double_t covarianceYY=sigmaYY + (-1.)*((sigmaXY*sigmaXY)/sigmaXX);
2107 Double_t covarianceYZ=sigmaYZ-(sigmaXZ*sigmaXY/sigmaXX);
2108 Double_t covarianceZZ=sigmaZZ-((sigmaXZ*sigmaXZ)/sigmaXX);
2110 Double_t newCov[15];
2111 newCov[0]=covarianceYY;
2112 newCov[1]=covarianceYZ;
2113 newCov[2]=covarianceZZ;
2114 for(Int_t i=3;i<15;i++){
2118 // set the new parameters
2120 Set(newX,fAlpha,newParam,newCov);
2125 void AliExternalTrackParam::CheckCovariance() {
2127 // This function forces the diagonal elements of the covariance matrix to be positive.
2128 // In case the diagonal element is bigger than the maximal allowed value, it is set to
2129 // the limit and the off-diagonal elements that correspond to it are set to zero.
2131 fC[0] = TMath::Abs(fC[0]);
2139 fC[2] = TMath::Abs(fC[2]);
2147 fC[5] = TMath::Abs(fC[5]);
2155 fC[9] = TMath::Abs(fC[9]);
2163 fC[14] = TMath::Abs(fC[14]);
2164 if (fC[14]>kC14max) {
2172 // The part below is used for tests and normally is commented out
2173 // TMatrixDSym m(5);
2177 // m(1,0)=fC[1]; m(1,1)=fC[2];
2178 // m(2,0)=fC[3]; m(2,1)=fC[4]; m(2,2)=fC[5];
2179 // m(3,0)=fC[6]; m(3,1)=fC[7]; m(3,2)=fC[8]; m(3,3)=fC[9];
2180 // m(4,0)=fC[10]; m(4,1)=fC[11]; m(4,2)=fC[12]; m(4,3)=fC[13]; m(4,4)=fC[14];
2183 // m(0,2)=m(2,0); m(1,2)=m(2,1);
2184 // m(0,3)=m(3,0); m(1,3)=m(3,1); m(2,3)=m(3,2);
2185 // m(0,4)=m(4,0); m(1,4)=m(4,1); m(2,4)=m(4,2); m(3,4)=m(4,3);
2186 // m.EigenVectors(eig);
2188 // // assert(eig(0)>=0 && eig(1)>=0 && eig(2)>=0 && eig(3)>=0 && eig(4)>=0);
2189 // if (!(eig(0)>=0 && eig(1)>=0 && eig(2)>=0 && eig(3)>=0 && eig(4)>=0)) {
2190 // AliWarning("Negative eigenvalues of the covariance matrix!");